The closest prior art is epitomized by the disclosure set forth in U.S. Pat. No. 951,172 which issued on Mar. 8, 1910. That patent clearly discloses incorporating an axial passage through the valve element to equalize the pressure acting on the opposite ends thereof so that the spindle forming the valve element can be more easily translated to effect opening and closing of the valve mechanism--specifically in the environment of a ballcock. At any given line pressure the prior art construction can be designed to work quite adequately, but it has been found that the valve will not open or close over a wide range of line pressures unless a full size ballfloat and lever are used, and even then as the line pressure increases the valve not only becomes progressively more difficult to open but also snaps more quickly closed, which produces relatively severe water hammer within the normal range of line pressures currently encountered.
Thus, the aforesaid U.S. Pat. No. 951,172 requires a rather extensive space within which to operate most effectively. Moreover, the prior art discloses the necessity of employing some mechanical means by which to retain the sealing washer in situ.